 Lactate is a key metabolic intermediate produced during aerobic respiration and serves as a source of energy for many cells. It has been shown to play a critical role in regulating cellular metabolism, growth and survival. Recently, it was discovered that lactate can be modified into a new form called lactylation, which is believed to have a significant impact on cellular metabolism and signaling. In this review, we summarise the current understanding of lactate and discuss how lactate and lactylation may contribute to the development of certain diseases such as cancer and inflammation. This article was authored by Xiaolu Li, Yan Yan Yang, Bei Zhong and others.